configfs: dir.c fix possible recursive locking
configfs_register_subsystem() with default_groups triggers recursive locking. it seems that mutex_lock_nested is needed. ============================================= [ INFO: possible recursive locking detected ] 2.6.24-rc6 #141 --------------------------------------------- swapper/1 is trying to acquire lock: (&sb->s_type->i_mutex_key#3){--..}, at: [<c40ca76f>] configfs_attach_group+0x4f/0x190 but task is already holding lock: (&sb->s_type->i_mutex_key#3){--..}, at: [<c40ca9d5>] configfs_register_subsystem+0x55/0x130 other info that might help us debug this: 1 lock held by swapper/1: #0: (&sb->s_type->i_mutex_key#3){--..}, at: [<c40ca9d5>] configfs_register_subsystem+0x55/0x130 stack backtrace: Pid: 1, comm: swapper Not tainted 2.6.24-rc6 #141 [<c40053ba>] show_trace_log_lvl+0x1a/0x30 [<c4005e82>] show_trace+0x12/0x20 [<c400687e>] dump_stack+0x6e/0x80 [<c404ec72>] __lock_acquire+0xe62/0x1120 [<c404efb2>] lock_acquire+0x82/0xa0 [<c43fdad8>] mutex_lock_nested+0x98/0x2e0 [<c40ca76f>] configfs_attach_group+0x4f/0x190 [<c40caa46>] configfs_register_subsystem+0xc6/0x130 [<c45c8186>] init_netconsole+0x2b6/0x300 [<c45a75f2>] kernel_init+0x142/0x320 [<c4004fb3>] kernel_thread_helper+0x7/0x14 ======================= Signed-off-by: Joonwoo Park <joonwpark81@gmail.com> Signed-off-by: Joel Becker <joel.becker@oracle.com> Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
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@ -546,7 +546,7 @@ static int populate_groups(struct config_group *group)
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* That said, taking our i_mutex is closer to mkdir
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* That said, taking our i_mutex is closer to mkdir
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* emulation, and shouldn't hurt.
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* emulation, and shouldn't hurt.
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*/
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*/
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mutex_lock(&dentry->d_inode->i_mutex);
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mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
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for (i = 0; group->default_groups[i]; i++) {
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for (i = 0; group->default_groups[i]; i++) {
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new_group = group->default_groups[i];
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new_group = group->default_groups[i];
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@ -1405,7 +1405,8 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys)
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sd = configfs_sb->s_root->d_fsdata;
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sd = configfs_sb->s_root->d_fsdata;
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link_group(to_config_group(sd->s_element), group);
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link_group(to_config_group(sd->s_element), group);
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mutex_lock(&configfs_sb->s_root->d_inode->i_mutex);
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mutex_lock_nested(&configfs_sb->s_root->d_inode->i_mutex,
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I_MUTEX_PARENT);
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name.name = group->cg_item.ci_name;
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name.name = group->cg_item.ci_name;
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name.len = strlen(name.name);
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name.len = strlen(name.name);
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